HOUSTON—When Wade Phillips coached the Dallas Cowboys, few people called him brilliant.

Perceptions can change quickly, especially when you change jobs. Phillips is doing a brilliant job as the Houston Texans’ defensive coordinator—a reason the Texans (6-1) are the team to beat in the AFC—a serious threat to reach their first Super Bowl.

It’s hard to overstate how important Phillips has been to the Texans’ franchise since he arrived before the 2011 season. Houston’s defense has morphed into one of the NFL’s best, as it proved again Sunday during a 43-13 thrashing of the Baltimore Ravens (5-2). Before Phillips showed up, coach Gary Kubiak was in danger of losing his job because no matter how well his offense played, the Texans’ defense couldn’t get its act together.

Sometimes a coordinator can make or break a staff, particularly when the head coach primarily oversees one side of the ball. Look at Philadelphia, where embattled coach Andy Reid just fired Juan Castillo as defensive coordinator. Look at Buffalo, where defensive coordinator Dave Wannstedt is overseeing one of the worst defenses money can buy.

The Texans clearly have the right person as defensive coordinator, a big part of the puzzle that makes them contenders. Houston linebacker Bradie James, who also played for Phillips in Dallas, loves the way Phillips has embraced being a coordinator again, knowing how hurt he was when the Cowboys dumped him as head coach in 2010.

“I think he’s having a great time, to be honest with you,” James said. “With the team that we have, all the characters that we have, he’s one of the characters. I’m having a good time, so I can see why he is. Being in Dallas is a whole different animal.’’

Being a defensive coordinator allows Phillips to focus on what he does best—coach defense. Phillips has molded the Texans’ unit into a terrorizing force. No coach can succeed without players, and the Texans have some special ones, such as defensive end J.J. Watt and cornerback Johnathan Joseph. However, the Texans have also lost a key piece in Brian Cushing, who is done for the season after suffering a knee injury, and Mario Williams, who was lost during free agency to the Buffalo Bills.

Yet, the Texans’ defense keeps rolling under Phillips. He is bothered by the general view that he is a terrific coordinator and a not-so-terrific head coach. But even if he can’t change what people think of him, Phillips can enjoy being the architect of an impressive defense.

“Evidently I don’t do as well as a head coach,’’ Phillips said with a slight smile in the Texans’ locker room. “Although my record (82-59 as a head coach) is a lot better than a lot of people think.

“The players got to respond to you, how you are, how you coach. They’ve always done that. I’ve had good relationships with players. I think it’s a great situation for me. I’m happy where I am, I’m enjoying this.’’

Not that the Texans’ defense is always dominant. Aaron Rodgers torched Houston’s defense for six TD passes a week ago during the Texans’ only loss. That’s part of what makes the NFL so intriguing. On a given week, even the best can play like the worst.

How the Texans responded to that beatdown, however, was telling. The Green Bay game was the Texans’ first without Cushing. Too many players tried to do too much in his absence, which made the Texans vulnerable to being picked apart by a great quarterback like Rodgers.

Against the Ravens, the Texans’ defense played as a unit again—and it was devastating. Ravens quarterback Joe Flacco was sacked four times and was clearly flustered in his worst performance of the season (21-of-43, 147 yards, 1 TD, two interceptions).

Ravens coach John Harbaugh was impressed, both by how good the Texans were and how physical they were.

“Sometimes you get tossed out of the bar,” Harbaugh said. “We kept running back in … they kept throwing us back out.”

To play a dominant defensive game without Cushing was huge for the Texans’ psyche. “It’s big for the rest of the season, because I think when you lose a player like Cush, it’s the human nature to say, ‘OK, how are we going to be?’ ” Kubiak said. “What we found out today is we can still play great defense and expect to do that the rest of the year.”

In five of their seven games, the Texans have given up 17 points or fewer. In today’s NFL, that is championship-caliber defense.

“If you’re 6-1 going into the bye, that’s a pretty good sign for your football team … if you’re playing at a high level,” Phillips said. “We really haven’t had any close games. We’ve been dominant in the games we’ve won.”

The Texans have a bye in Week 8, followed by a Week 9 home game against the Bills. With the Texans playing in the not-so-tough AFC South, it’s not hard to imagine them finishing with the best record in the AFC, which would give them home-field advantage in the playoffs.

Phillips may never get another shot as a head coach. But the way the Texans’ defense is playing, Phillips may never have a better shot at reaching the Super Bowl.